Retaining device for an electric motor

ABSTRACT

In known retaining devices for electric motors, rotationally flexible retaining elements on the order of leaf springs are provided between a receiving housing and the electric motor and serve to decouple noise of the electric motor. The novel retaining device for an electric motor includes retaining elements that extend axially between a receiving housing and the motor housing. These retaining elements enable low-frequency decoupling below the frequencies to be decoupled; on the occurrence of natural resonance when the electric motor is turned on and off or there are shocks from outside, the torsional motion of the retaining elements is limited by stop elements. The retaining device is especially well suited to electric motors of blowers.

The invention is based on a retaining device for an electric motor bythe preamble to.

A retaining device for an electric motor is already known (U.S. Pat. No.4,063,060), in which three rotationally flexible retaining arms on theorder of leaf springs are provided. The retaining arms are deployed inradiating fashion between the electric motor and the receiving housing,offset from one another by equal circumferential angles, and are eachsecured rigidly by one end to the electric motor and by the other end,with the interposition of elastic buffers. The retaining arms are joinedto an inlet collar that is firmly connected to the receiving housing.These retaining arms effect an elastic binding of the electric motor tothe receiving housing and thus damp the transmission of running noiseand operation-dictated vibration of the blower to the receiving housing,caused for instance by imbalance in the blower wheel, so that aconsiderable reduction in noise development is achieved. By means of thethree-point suspension of the electric motor in a single plane and thelow spring constant of the retaining arms in the direction of torsion,the motor executes relatively major vibration and tilting motions, whichin the elastic elements, especially the buffers, induce shear forcesthat rapidly cause material fatigue and damage. The service life of thisknown retaining device is therefore relatively limited and is inadequatefor use in motor vehicles, in which the elastic elements must alsoabsorb vibration caused by shocks from the roadway to the electricmotor.

In one such retaining device in accordance with U.S. Pat. No. 4,161,667,the retaining arms on the order of leaf springs each have a respectiveaxial portion, between their two ends, that extends in the direction ofthe motor pivot axis.

A retaining device is also known (German Utility Model DE 91 08 745 U1)with a receiving housing into the receiving opening of which a motorhousing of an electric motor protrudes. An intermediate bush is slippedonto the motor housing with radial spacing and is firmly retained byspring tongues. Between the receiving housing and the intermediate bush,a retaining body made of plastic is fastened; with an encompassingannular part it engages the receiving housing and the intermediate bush,and its three arm portions beginning at the annular part and extendingaxially rest on the receiving housing and, with a radial end portion,engage the intermediate bush.

German Patent Disclosure DE 27 27 119 A1 also discloses a retainingdevice in which spring-elastic retaining elements are joined on one endto a tubular retaining ring that force-lockingly engages the motorhousing.

An object of the invention is to create a retaining device in whichnoise decoupling of the electric motor is done at such low frequenciesthat the resonant frequency of the spring-mass system formed by theelectric motor and the retaining device is below the frequencies of theelectric motor to be decoupled; even in rough operation in the motorvehicle, excessive stress on the retaining device does not occur, thusguaranteeing a long service life for the retaining device.

By disposing one stop element in the region of each retaining element,which stop element limits the amplitude of the vibrational motion of theretaining elements relative to the receiving housing, it is assured thatin the case of resonance, for instance upon starting of the electricmotor and when it is turned off or upon acceleration from outside fromimpacts and shocks, the maximum possible deflection of the electricmotor relative to the receiving housing is limited, thus precludingexcessive strain on the retaining device.

It is advantageous that by the disposition of two stop faces facing oneanother, the amplitude of the torsional motion of the retaining elementsrelative to the receiving housing upon a clockwise or counterclockwiserotation is limited.

It is also advantageous that the two stop faces, facing one another inthe direction of the rotary motion, of the stop elements extend in sucha way, in particular with a curved course, that upon a vibrationalmotion a first portion of the axial portion, oriented toward the firstend of the retaining element, comes to rest with a greater amplitude onone of the stop faces than a second portion oriented toward the secondend; as a result the spring rate of the retaining elements increases, inparticular progressively, with increasing deflection, and thus theresonant rise is reduced. It is also advantageous to embody the axialportions of the retaining elements with a rectangular cross section andto subdivide the axial portion by means of a transposition into a firstsubportion, which is oriented toward the first end, and a secondsubportion, which is oriented toward the second end, and in the firstsubportion the transverse sides and in the second subportion thelongitudinal sides of the rectangular cross section face the motorhousing and the receiving housing, as a result of which, by this changein the geometry of the retaining elements, the spring rate of theretaining elements in various directions (axially, radially, thetorsional direction) can be varied, and an adaptation of the springcharacteristics of the retaining elements to decouple the vibrationoccurring in various directions is possible.

It is also advantageous to embody a transverse stop face on the stopelement that is embodied in the region of the second end of theretaining element and that extending toward the first end has adecreasing spacing from the retaining element, in order to limit themaximum vibrational amplitude of the retaining elements in the radialdirection.

The integral embodiment of the stop elements on the receiving housing isadvantageous in the sense that no additional assembly steps are neededto install the stop elements, while embodying the stop elements as anindependent part has the advantage that if there is a need to change thestop geometry, no changes of tools for producing the receiving housingare needed.

The embodiment of the cup-shaped receiving housing with a cylindricalpart and a bottom part, and the joining of the retaining elements,extending axially to the motor pivot axis, to a tubular retaining ringand a retaining disk enable an especially compact design of theretaining device.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are shown in simplified form inthe drawings and described in further detail below.

FIG. 1 shows a retaining device with an electric motor along a line I--Iof FIG. 2;

FIG. 2 is a plan view on a retaining device with an electric motor;

FIG. 3 is a section taken along the line III--III of FIG. 1;

FIG. 4 is a section taken along the line IV--IV of FIG. 3;

FIG. 5 is a section taken along the line V--V of FIG. 3;

FIG. 6 is a fragmentary view of a retaining device with a stop elementacting in the radial direction.

In FIG. 1, an electric motor 1 is shown that is used in particular as ablower motor in a motor vehicle.

The electric motor 1 has a shaft 3, protruding out of a motor housing 2,that is connected to a fan wheel 4 and is supported rotatably about amotor pivot axis 5. The motor housing 2 protrudes at least partway intoa receiving opening 8 of a cup-shaped receiving housing 9, which has anannular cylindrical part 10 and a radially extending bottom part 11. Ascan also be seen in FIG. 2, which shows a plan view without thefanwheel, the receiving housing 9, on its end remote from the bottompart 11 has a retaining flange 12, which begins at the annularcylindrical part 10 and extends radially outward, with fasteningopenings 13 for fastening (not shown) the receiving housing 9 in themotor vehicle by means of screws.

The motor housing 2, extending coaxially with the motor pivot axis 5,protrudes with radial spacing into the receiving opening 8 of thereceiving housing 9. Extending in this annular interstice, formed by theradial spacing, between the circumference of the motor housing 2 and thewall of the receiving opening 8 are at least three spring-elasticretaining elements 16 that are circumferentially spaced apart from oneanother and are freely movable; with their first ends 17, located at thetop in the view of FIG. 1, they are joined to a tubular retaining ring18, which embraces the circumference of the motor housing 2 and issecured to the motor housing 2, for instance by shrinkage, gluing,riveting, screwing, or the like. Beginning at the first end 17, an axialportion 19 of the retaining element 16 extends downward, in terms of theview in FIG. 1, as far as a second end 20, which is connected to arespective retaining disk 21 that extends radially inward, parallel tothe bottom part 11 of the receiving housing 9. The retaining disk 21,like the bottom part 11, has through openings 24, through which screws25 are inserted in order to fix the retaining disk 21 to the bottom part11.

The spring-elastic retaining elements 16 have a rectangular crosssection, for instance, and extend with their axial portion 19 in thedirection of the motor pivot axis 5 in such a way that in the positionof repose of the electric motor 1, the axial portions 19, both in theradial direction and the circumferential direction, have a radialspacing from the receiving opening 8 of the receiving housing 9 and themotor housing 2 and can also execute motion freely in thecircumferential direction. Together with the retaining ring 18, theretaining disk 21 and the receiving housing 9, the retaining element 16,for instance three in number offset from one another by 120°, form aretaining device for the electric motor 1 that allows a torsional motionof the electric motor 1 relative to the receiving housing 2. Thereceiving housing 9 and the retaining elements 16 are made of plastic,for instance, and the retaining elements 16, retaining ring 18 andretaining 21 are embodied integrally in one component. Thespring-elastic retaining elements 16, together with the electric motor1, form a so-called spring-mass vibration system, which upon excitationof the electric motor 1 is set into torsional vibration that leads toundesired noise in the motor vehicle. The spring rate of the retainingelements 16 is selected such that taking into account the mass of theelectric motor 1, a low-frequency (for instance, 10 Hz) resonantfrequency results. When the electric motor is driven for instance at 50Hz, the disturbing vibrations to be decoupled are then in the so-calledsupercritical range, far above this resonant frequency, and areoptimally decoupled toward the motor vehicle. The result is a torsionalmotion of the electric motor 1 about the second ends 20 of the retainingelements 16.

However, there are also operating states, for instance upon accelerationfrom outside from shocks and impacts during motor vehicle operation orwhen the electric motor 1 is started up or stopped, in which the naturalresonant frequency of the spring-mass vibration system, comprising theretaining elements 16 and the electric motor 1, is traversed, so thatnoise development at high torsional amplitudes can occur, which can alsoentail damage. In the region of each retaining element 16 on thereceiving housing 9, a stop element 28 is therefore provided, which upona clockwise or counterclockwise rotation limits the amplitude of thetorsional motion of the retaining elements 16 relative to the receivinghousing 9 by means of two stop faces 29, facing one another. The stopelements 28 may be embodied integrally as U-shaped recesses in thereceiving opening 8 of the receiving housing 9, or as part of thereceiving housing 9, or the stop elements 28 may be disposed asindividual separate U-shaped parts in the receiving opening 8 of thereceiving housing 9 and secured to that housing. As shown in FIG. 4, thestop faces 29 of the stop elements 28 extend such that the two stopfaces 29 facing one another are spaced apart by a lesser distance, inthe region of the second end 20 of the axial portion 19 of the retainingelements 16, than in the region of the first end 17 of the retainingelements 16, so that upon a vibrational motion, a first portion 30 ofthe axial portion 19 toward the first end 17 of the retaining element 16comes to rest with a greater amplitude on the stop face 29 than a secondportion 31 of the axial portion 19 toward the second end 20. Thus thedisposition of stop elements 28 with stop faces 29 assures protection ofthe retaining device in the case of resonance or influences fromoutside, since if such conditions occur, upon a torsional motion, theretaining elements 16 are gently caught by the stop faces 29 and guardedagainst a destructive overload. In the exemplary embodiment of FIG. 5the contour of the two stop faces 29 of a stop element 28 is curved insuch a way that toward the first end 17 of the retaining element 16,they have a greater spacing from one another than toward the second end20 of the retaining element; the course of the contour of each stop face29 is selected such that the second portion 31 of the axial portion 19already comes to contact the stop face 29 at a lesser amplitude of thetorsional motion, so that the spring rate or spring stiffness of thefirst portion 30, which can still execute a greater amplitude oftorsional motion until it contacts the stop face 29, increases and inparticular has a progressively increasing course. Thus the springcharacteristics of the retaining elements 16 and the maximum possibledeflection of the electric motor 1 upon a torsional motion can beoptimally designed to avoid an overload on the retaining device.

As shown in FIG. 3, the retaining elements 16 have a rectangular crosssection with two short transverse sides 34, which are oriented towardthe receiving housing 9 and the motor housing 2, and two longerlongitudinal sides 35, which are each oriented toward one of the stopfaces 29 of the stop element 28 and in other words extend radially. Asalready noted, the retaining elements 16, the retaining ring 18 and theretaining disk 21 may be made from plastic, but they may also be made ofmetal as individual parts, as shown in FIG. 6, and then joined togetherby welding or soldering. A change in this spring geometry of theretaining element 16 in various directions is attainable by varying thecross-sectional geometry of the retaining element 16. To that end, theretaining element 16, for instance, embodied with a rectangular crosssection is provided with a transposition 36 in its axial portion 19 thatsubdivides the axial portion into a first sub portion 37, which isoriented toward the first end 17, and second sub portion 38, orientedtoward the second end 20. In the first subportion 37 the transversesides 34, and in the second subportion 38 the longitudinal sides 35,face the motor housing 2 and the receiving housing 9, as a result ofwhich the second subportion of the retaining element 16 is embodiedresiliently in the radial direction, while the first subportion 37resiliently enables torsional motions. The transposition 36 provided inFIG. 6 is independent of the choice of material, for retaining elements16 made from plastic or metal. To limit the radial amplitude of theretaining element 16, a transverse stop face 39, oriented toward themotor housing 2 on the stop element 28, for instance, is provided, whichextends for instance in the region of the second subportion 38 and isspaced apart by a decreasing spacing relative to the retaining element16 in the direction from the first end 17 of the retaining element 16toward the second end 20 thereof.

The foregoing relates to a preferred exemplary embodiment of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

What is claimed is:
 1. A retaining device for an electric motor, inparticular an electric motor for a blower, comprising a receivinghousing that has a receiving opening, a motor housing of the electricmotor extends into said receiving opening coaxially to a pivot axis ofthe motor, said motor housing protrudes with radial spacing at leastpartway, and includes at least three spaced-apart spring-elasticretaining elements, each of said retaining elements have one first endand one second end, in which the retaining elements (16), between thefirst end (17) and the second end (20), have at least one axial portion(19), which extends in a direction of the motor pivot axis (5), whereinthe retaining elements are joined by their first ends to the motorhousing and by their second ends to the receiving housing which allows avibrational motion of the electric motor relative to the receivinghousing, a stop element (28) limits the amplitude of a vibrationalmotion of the electric motor (1) relative to the receiving housing (9)in a region of each retaining element (16) on the receiving housing (9).2. The retaining device according to claim 1, in which the stop element(28) has two stop faces (29) facing one another, which upon clockwise orcounterclockwise rotation limit a torsional motion of the electric motor(1).
 3. The retaining device according to claim 2, and the stop faces(29) extend in such a way that upon a torsional motion, a first portion(30) of the axial portion (19) oriented toward the first end (17) of theretaining element (16) comes to contact the stop face (29) with agreater amplitude than a second portion (31), oriented toward the secondend (20), of the axial portion (19).
 4. The retaining device accordingto claim 3, in which the two stop faces (29), facing one another, of thestop element (28) extend in curved fashion, in such a way that towardthe first end (17) of the retaining element (16), the two stop faceshave a greater spacing from one another than toward the second end (20)of the retaining element (16).
 5. The retaining device according toclaim 4, in which the axial portion (19) of the retaining element (16)has a rectangular cross section, with two transverse sides (34) and twolongitudinal sides (35) which are longer than the transverse sides, andis subdivided by a transposition (36) into a first subportion (37),which is oriented toward the first end (17), and a second subportion(38), which is oriented toward the second end (20), and in the firstsubportion (37) the transverse sides (34) and in the second subportion(38) the longitudinal sides (35) face the motor housing (2) and thereceiving housing (9).
 6. The retaining device according to claim 3, inwhich the axial portion (19) of the retaining element (16) has arectangular cross section, with two transverse sides (34) and twolongitudinal sides (35) which are longer than the transverse sides, andis subdivided by a transposition (36) into a first subportion (37),which is oriented toward the first end (17), and a second subportion(38), which is oriented toward the second end (20), and in the firstsubportion (37) the transverse sides (34) and in the second subportion(38) the longitudinal sides (35) face the motor housing (2) and thereceiving housing (9).
 7. The retaining device according to claim 2, inwhich the stop element (28) has a transverse stop face (39), toward themotor housing (2), which has a decreasing spacing from the retainingelement (16) in the direction extending from the first end (17) of theretaining element (16) to the second end (20).
 8. The retaining deviceaccording to claim 2, in which the stop element (28) is embodiedintegrally on the receiving housing (9).
 9. The retaining deviceaccording to claim 2, in which the stop element (28) is connected as anindependent part to the receiving housing (9).
 10. The retaining deviceaccording to claim 2, in which the first ends (17) of the retainingelements (16) are joined to a tubular retaining ring (18), whichembraces the motor housing (2) and can be fixed on the motor housing(2).
 11. The retaining device according to claim 10, in which theretaining elements (16) are made of plastic integrally with theretaining ring (18).
 12. The retaining device according to claim 1, inwhich the stop element (28) has a transverse stop face (39), toward themotor housing (2), which has a decreasing spacing from the retainingelement (16) in the direction extending from the first end (17) of theretaining element (16) to the second end (20).
 13. The retaining deviceaccording to claim 1, in which the stop element (28) is embodiedintegrally on the receiving housing (9).
 14. The retaining deviceaccording to claim 1, in which the stop element (28) is connected as anindependent part to the receiving housing (9).
 15. The retaining deviceaccording to claim 1, in which the receiving housing (9) is cup-shaped,with an annular cylindrical part (10) and a radially extending bottompart (11), and the second end (20) of each retaining element (16) isjoined to the bottom part (11).
 16. The retaining device according toclaim 15, in which the second ends (20) of the retaining elements (16)are joined to a retaining disk (21), which extends parallel to thebottom part (11) of the receiving housing (9) and can be fixed to thebottom part (11).
 17. The retaining device according to claim 16, inwhich the retaining elements (16) are made of plastic integrally withthe retaining disk (21).
 18. The retaining device according to claim 1,in which the first ends (17) of the retaining elements (16) are joinedto a tubular retaining ring (18), which embraces the motor housing (2)and can be fixed on the motor housing (2).
 19. The retaining deviceaccording to claim 18, in which the retaining elements (16) are made ofplastic integrally with the retaining ring (18).
 20. The retainingdevice according to claim 19, in which the retaining elements (16) aremade of plastic integrally with the retaining disk (21).